The present disclosure relates to connection reestablishment methods and apparatus. In one example method, when a handover fails, a terminal reverts back to a source configuration, and obtains a selected cell. The terminal sends a connection reestablishment request to a selected radio access network device. The terminal receives a first message from the selected radio access network device, where the first message includes indication information used to indicate to derive an access network key based on a core network key. The terminal obtains a first core network key based on the indication information, and derives a first access network key based on the first core network key. The terminal communicates with the selected radio access network device by using the first access network key.